The clinical and molecular characteristics of invasive Streptococcus agalactiae diseases in nonpregnant adults in Taiwan

Abstract

Background: Streptococcus agalactiae (Group B Streptococcus, GBS) is a growing threat to nonpregnant adults. We aimed to describe the clinical and molecular characteristics of invasive GBS infections in adults. Methods: All adults with invasive GBS infections at a tertiary-level medical center in Taiwan between 2014 and 2020 were analyzed. Capsule serotyping, multilocus sequence typing and antibiotic susceptibility testing were performed. Results: A total of 666 adults with GBS infections were analyzed. The median age at onset was 65 years (range 19–102). The most common manifestation was bacteremia without focus (80.4 %). The younger patients (19–39 years old) had a significantly higher rate of non-bloodstream infections (24.6 %, P < 0.001) and were overweight in most cases (77.2 %). Most patients had underlying chronic comorbidities (82.3 %). Capsular types VI (33.0 %), Ia (19.4 %), III (15.0 %), and V (10.2 %) were predominant. Clonal complexes (CCs) 1, 12, 17, 19, 23 and 452 accounted for 96.3 % (464/482) of the cases. All GBS isolates were susceptible to β-lactam antibiotics. The rates of resistance to erythromycin and clindamycin were 42.6 % and 39.2 %, respectively, but were especially high in type III, Ib and V GBS isolates. The mortality rates at one month and one year were 5.0 % and 12.3 %, respectively, but were significantly higher in elderly patients. Conclusion: The clinical manifestations of invasive GBS infections in adults are diverse. Elderly patients are susceptible to invasive GBS infections and have a relatively high mortality rate. Continuous surveillance of GBS epidemiology should be enforced given the increasing growing importance of antibiotic-resistant GBS isolates.